Memory devices are common in electronic systems and computers to store data. These memory devices may be volatile memory, where the stored data is lost if the power source is disconnected or removed, or non-volatile, where the stored data is retained even during power interruption. An example of a non-volatile memory device is a programmable metallization cell (PMC).
A PMC utilizes a fast ion conductor such as a chalcogenide-type or an oxide-type (e.g., NiO) and at least two electrodes (e.g., an anode and a cathode) with the fast ion conductor between the electrodes. When a voltage is applied across the electrodes, superionic clusters or conducting filaments rapidly grow from the cathode through the fast ion conductor towards the anode. When the clusters or filaments are present, the cell is in a low resistance state. When an electric field of opposite polarity is applied across the electrodes, the conducting filaments dissolve and the conducing paths are disrupted, providing the cell with a high resistance state. The two resistance states are switchable by the application of the appropriate electric field and are used to store the memory data bit of “1” or “0”.
While a high ionic conductive solid electrolyte (e.g., chalcogenide) provides a high speed switch between the two resistance states of the PMC, this material can suffer from poor data state retention. Another lower ionic conductive solid electrolyte (e.g., oxide electrolyte) provides for good data state retention, but this material can suffer from slow switching between the two resistance states of the PMC. Thus, there is a tradeoff between switching speed and data retention in a PMC cell depending on what solid electrolyte (in regards to the material property differences) is provided in the PMC cell. There is a need for a PMC cell that can provide both fast switching speeds and extended data retention.